Petroleum based heavy fuels are typically produced by the thermal distillation of crude petroleum in apparatus referred to as crude oil distillation towers. Distillates from such towers include gas, gasoline, naphtha, kerosene, gas oil, and diesel oil. The residue or bottoms from the distillation can either be coked in delayed coking drums at temperatures between 900.degree. to 930.degree. F. to produce coke and distilled overhead products or can be shipped and sold directly to be used as fuel in boilers on ships or in power or steam plants.
Industrial fuel oils can also consist of one or more of the following products derived from petroleum: vacuum tower bottoms, catalytically cracked light or heavy gas oils and catalytically cracked clarified oil. A No. 6 fuel oil is an example of such a product. It will typically have a boiling point of 660.degree. F., a specific gravity greater than 1.0.degree. and 45.degree. F. pour point. These products can contain significant amounts of H.sub.2 S.
When "sour" crude oils, i.e., those containing sulfur-containing components, are distilled, such components distribute into both the various distillation products and also to the residue or bottoms in the distillation unit. In the overhead or distillate products, the sulfur components of the crude oil contain mercaptans (thiols) and organodisulfides, but little if any H.sub.2 S. Numerous proposals have been made to "sweeten" such sour distillate products by treatment with a variety of additives. Disclosures illustrative of these are contained in U.S. Pat. Nos. 2,671,048 issued 2 Mar. 1954 (addition of phenylenediamine together with an organic base compound); 4,430,196 issued 2 February 1984 (addition of dimethylaminoethanol and/or dimethylisopropanolamine to the crude oil or the refinery stream products), and 4,594,147 issued 10 June 1986 (treating sour gasoline with choline).
None of the above proposals deal with the problem of H.sub.2 S in the atmosphere above or associated with sour heavy fuel oils. When such oils are to be used as fuel in industrial boilers or in electric utility steam plants or elsewhere, the presence of large amounts of H.sub.2 S in the atmosphere above or associated with the oil during transit in barges or ships, or in storage in refinery tanks or user tanks, constitutes a hazard to personnel who are in the vicinity of the storage or transport facilities. Typically, the H.sub.2 S specification for such fuel oils in 100 ppm or less. Since some of such oils may contain up to 5,000 ppm of H.sub.2 S, there is a need for an efficacious and economical method for reducing the H.sub.2 S concentration in the sour fuel oil atmosphere without affecting the burning properties of the fuel.